Automatic garage door openers are commonly powered by electric motors actuated by manual, momentary closing of electric switches, the motors being then maintained in operation by holding circuits until the door is fully open or fully dosed, at which time limit switches function to stop the motors. A disadvantage of this system has been that the operator may press the button without first being sure that the door opening is free of obstructions, or he may press the button and then walk away, with the result that an obstruction such as a person or an automobile may move into the path of the closing door, with the consequence of injury or damage.
The problem described is often resolved by providing a door operating system of the class described with the addition of control means operable to stop the operating motor automatically if any obstruction enters or approaches the door as it is being closed. This is often accomplished by providing light beams positioned to traverse the door opening, and the approaches thereto, and photoelectric cells energized by the light beams to close circuits maintaining the motor in operation, whereby if any of the light beams are interrupted, the motor will be stopped.
The prior art provides for such means to be integrated into the design, and communicate with the board electronics, of automatic garage door opener systems. This presents a problem with garage door opener designs that are not equipped with such safety systems, particularly older designs. Furthermore, automatic garage door openers that are equipped with safety systems may eventually require replacement or updating to meet particular regulatory requirements, and in such cases, it can be difficult and/or costly to replace or retrofit these systems with safety systems.
Therefore, what is needed is a universal safety system that may be adapted for use with any automatic garage door opener.